miR-122-5p attenuates the inflammatory response by modulating microglia polarization after traumatic brain injury / 中华急诊医学杂志

ABSTRACT

Objective:To determine the effect of miR-122-5p on microglia polarization, apoptosis and inflammation after traumatic brain injury (TBI).Methods:A mouse model and an in vitro TBI model were established. Astrocytes were stimulated to synthesize and release exosomes by brain extracts. microRNA microarray analysis was used to analyze the significantly altered microRNAs. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was applied to detect the expression of miR-122-5p in the in vivo and in vitro TBI model. TUNEL, immunofluorescence, and Western blot were performed to detect the effects of miR-122-5p inhibitors on microglia apoptosis, microglia M1/M2 phenotype transformation and the activation of NLRP3 inflammasome pathway and the phosphorylation of NF-κB after TBI.Results:The results of microRNA microarray analysis showed that 83 miRNAs were downregulated significantly (altered more than 2 folds, P < 0.05), among which miR-122-5p was significantly down-regulated ( P < 0.01). Expression of miR-122-5p was significantly decreased in the in vivo and in vitro TBI model [(1.00±0.00) vs. (0.41±0.15), P < 0.001; (1.00±0.00) vs. (0.34±0.07), P < 0.001]. TUNEL and immunofluorescence showed that miR-122-5p inhibitor significantly alleviated microglia apoptosis[(8.03±1.30) vs. (3.17±0.34), P < 0.001] and promoted microglia M1→M2 phenotype transformation ,M1 phenotype polarization was reduced [(56.96±13.70) vs. (34.70±3.47), P =0.002] and M2 phenotype polarization was increased [(30.46±3.67) vs. (40.74±2.49), P =0.005]. Western blot showed that NLRP3 inflammasome activation was inhibited and NF-κB phosphorylation was decreased when miR-122-5p was downregulated[(0.77±0.10) vs. (0.51±0.11), P =0.02; (0.73±0.08) vs. (0.50±0.07), P =0.003]. Conclusions:miR-122-5p is downregulated in microglia and exosomes secreted by astrocytes after TBI. miR-122-5p inhibitor can attenuate the microglia inflammatory response after TBI by inhibiting the activation of NLRP3 inflammasome pathway and the phosphorylation of NF-κB, promoting the microglia M1→M2 phenotypic transformation and reducing microglia apoptosis, thereby reducing the microglia inflammatory injury after TBI.